The present invention refers to a method for classifying seeds, in particular sugar-beet seeds, by the use of infrared-spectroscopy. One focus of the classification is an improvement of the seed quality characteristics, in particular the field emergence characteristics of sugar-beet seeds.
Sugar-beet is a cultivated plant of Beta vulgaris which is a plant whose root contains a high concentration of sucrose. It is grown commercially for sugar production. The sugar comes from the taproot of the beetroot plant, chard and fodder beet, all descended by cultivation from the sea beet. Beet sugar accounts for 30% of the world's sugar production.
The flowering habit of sugar beet leads to a very heterogeneous mix of seed quality in the harvested ready seed (i.e., raw seed). One example of a seed quality that needs to be controlled in order to meet market requirements and that requires a strict selection of the seeds having a certain quality is, for example, field emergence performance.
Despite the likeness of the seeds from the outside they do not form a homogeneous fraction but are quite different in their characteristics, such as, for example, field emergence characteristics which is a collective name for features like viability (i.e., final population at normal field-conditions), growth-rate (i.e., speed of early emergence) and vigour (i.e., final population at stressed field-conditions). The result of the heterogeneity in field emergence characteristics in a seed lot could be loss of harvest, reduction of sugar-beet quality due to heterogeneous root size and unpredictability of expected crop yield.
For example the early emergence of a seed can occur after about 50-60 day degrees, but on average the first emergence appear after about 80 to 110 day degrees in a normal population. However, several seed will not emerge at all, i.e., no sugar beet plants will grow.
One reason for these differences in field emergence characteristics of sugar beet seeds are abnormal seeds, like empty seeds, twin-embryos or seeds with free space(s) inside or partially filled seeds which account for the heterogeneity of the natural seed fractions.
Since said quality-differences are nearly impossible to deduce from the outside, due to the fact that the sugar beet seed is hidden inside a fruit wall, classification and/or sorting are difficult to perform.
In commercial seed production therefore the problem arises, that only a fraction of the seeds shows the desired field emergence characteristics. It is not unlikely that up to 70% of the raw seed from a production does not show a certain seed quality, like for example field emergence characteristics, and need to be discarded.
Therefore, it would be a great improvement in terms of productivity and cost/value ratio, if the percentage of seeds which show the desired field emergence characteristics could be increased in commercial seeds.
In the prior art different techniques for seed characterisation and/or sorting have been developed.
Mukasa et al., Plant Prod. Sci. 8 (1): 3-7 (2005) evaluates the water content and true weight of sugar-beet seeds by NIR. However, this method is a rather imprecise technique and has been shown to be inappropriate to predict seed quality characteristics.
Soltani, A., Improvement of Seed Germination of Fagus orientalis Lipsky. ISSN 1401-6230, ISBN 91-576-6509-5 describes the improvement of seed germination of oriental beech by NIR-analysis. However, again the author focused only on one particular aspect of the seeds, namely their germination characteristic. Complex characteristics, such as field emergence characteristics, have not been disclosed.
Mittler et al., “Hohe Saatgutqualität für leistungsfähige Bestände”, Zuckerrübe 2004, Vol. 53 evaluates the quality of seeds with X-ray techniques. However, the classification of seeds with X-ray is time-consuming, expensive and difficult to automate.
EP 1 578 544 B1 describes sorting means to sort “objects” and “granules”, as for example plastic parts, pills, beads, grains, beans and the like. Sorting for complex characteristics, such as field emergence characteristics, have not been disclosed.
EP 1 401 589 B1 describes sorting means to sort objects comprising organic material. Sorting for characteristics, such as field emergence characteristics, have not been disclosed.
Dowell et al., Cereal Chem. 83 (5):537-543, Dowell et al., Cereal Chem. 86(5):527-533 and Tønning et al., Cereal Chem. 86(6):706-713 use sorting means for post-harvest quality control and/or improvement with respect to further processing of different crop, primarily wheat or other cereals.
US 2004/0055211 uses a method for determining viability or non-viability of seeds from Pinus sylvestris L. Methods for discriminating different complex seed qualities within the fraction of viable seeds are not disclosed. Tigabu and Odén (New Forests (2003) 25: 163-176) use a method to discriminate between viable and empty seeds of Pinus patula. Again, methods for discriminating between different complex seed qualities within the fraction of viable seeds are not disclosed.
WO 2010/000266 also discloses a method for discriminating between viable and non-viable seeds. Seeds are sorted according to categories like “filled, but dead”, “infested”, “infected”, “empty”, or the like (cf. p. 15, lines 17-19). Also in this publication no methods for discriminating different complex seed qualities within the fraction of viable seeds are disclosed.
Thus, the prior art methods do not allow to sort for seeds based on complex quality characteristics. Especially methods for discriminating different complex seed qualities of viable seeds are not disclosed.
In view of the above, one object of the invention was to find a method which allows for both fast and cheap analysis of the seeds as well as a sufficiently accurate classification of viable seeds according to complex quality characteristics, such as field emergence characteristics.
The present invention solves this problem.